1. Field of the Invention
This invention relates to a veneer lathe for peeling a wide, thin veneer from a log by a knife laid along the log by holding the log in position and rotating it about its axis by means of spindle chucks applied fast one each to the opposite end faces of the log and pressing the knife against the periphery of the log in rotation. More particularly, this invention relates to a veneer lathe which is capable of eliminating the phenomenon of curling, namely the inclination that the freshly peeled veneer will turn upwardly owing to stress and other factors during the process of peeling, and which therefore is capable of increasing the yield of a high-quality veneer usable as face and back veneers in plywood which determines the commercial value of the finished plywood.
2. Description of the Prior Art
The veneer cut by and discharged from the conventional veneer lathe is liable to produce cracks on the rear side thereof and deviate upwardly from its predetermined course owing to the stress and other impacts generated during the process of peeling. The curl thus imparted to the veneer constitutes an obstacle to various works to be performed on the veneer subsequently to the work of peeling by the veneer lathe, making it difficult to materialize automation of a plywood production line or formation of a continuous flow of a plurality of production steps.
To mend the curl which persists in the freshly peeled veneer, there has prevailed a practice of installing immediately next to the veneer lathe an independent tenderizing machine provided with a rotary member having a multiplicity of sharp spikes implanted in the peripheral surface thereof and forcibly passing the freshly peeled veneer through the tenderizing machine.
As disclosed in U.S. Pat. No. 4,221,247 there has recently been developed a veneer lathe such that a veneer is peeled from a log by rotating, while in tight contact with the periphery of the log, discs each provided on the circumferential periphery thereof with a multiplicity of blades similar to the teeth of a saw thereby causing the blades on the discs to inflict stab wounds in the veneer and, at the same time, forcibly rotating the log against a knife advanced at a fixed rate toward the axis of the log, and the curl persisting in the veneer just peeled by and discharged from the knife is mended by bending the veneer below a pressure bar frame thereby forcibly producing cracks in the front side of the veneer to counterbalance the cracks first sustained in the rear side.
When the veneer lathe is provided with a tenderizing device or discs incorporating saw-toothed blades, however, the produced veneer inevitably sustains numerous stab wounds. When the veneer is peeled from a brittle log or the veneer is produced in a very small thickness of less than 1 mm, for example, such stab wounds may possibly develop into tears while the freshly peeled veneer is in transit. The veneer sustaining such tears cannot be used in the outermost plies in a plywood which determine the commercial value of the produced plywood. Even when it is used in the inner plies of a plywood, the plywood is obtained in low yield.
Further when the tenderizing device is installed immediately next to the veneer lathe, the addition of this device fairly increases the overall size of the veneer production equipment and the veneer production cost as well.